Study on Heat Transfer Characteristics of Gaseous Flows in Micro Channels

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Fabrication of small devices has increased the need for understanding of fluid flow and heat transfer in micro geometries. The pressure drop of fluid flow in a micro channel is quite large because of the friction loss. In case of gaseous flows, gas expands along the channel and flow is accelerated in the channel. This results in temperature fall due to the energy conversion from the internal energy to the kinetic energy. Heat transfer characteristics of gaseous flow in a micro channel might differ from that of incompressible flows. However, there is no parametric study on the heat transfer characteristics of gaseous flow in micro-channels. This is the motivation of the present study. Objectives of the present study are; 1. To obtain the heat transfer characteristics of gaseous flow in micro channels. 2. Verification of the gas temperature at the channel exit that has been numerically obtained in a foregoing research.(1) The computations are performed for channels with constant heat flux which ranges from 10^2 to 10^4W m^<-2> and with the constant wall temperarure. The channel height ranges from 10 to 100μm and the aspect ratio of the channel height and length is fixed at 200. The heat transfer characteristics of gaseous flow in a micro channel is obtained. The wall and bulk temperatures in micro-channels are compared with that of the incompressible flow in the conventional sized parallel plate channel. The heat transfer characteristics of a micro tube is also obtained.(2) The gas temperature at the exit of a micro tube was measured by a laser-induced fluorescence method and the comparisons were made with numerically obtained temperature in a foregoing research. And the availability of the laser-induced fluorescence method for temperature measurements is discussed.